Cellulose diacetates (CDAs) are used in many applications from filter tow and plastics to pharmaceuticals and coatings. These CDAs are generally prepared by the acetylation of cellulose to the triacetate and then back hydrolyzed to the required DS/AGU. Currently plasticized cellulose triacetate (CTA) is used as a film base for photographic films, movie films, some graphic arts films, and in the USSR for some X ray films. From films that contain silver (B&W films, some graphic arts film, and X ray film) the silver is recovered. No large use of the CTA film base in areas other than these has been developed.
Josef Fabian in a Czech. patent (Cs 155,036 (1972): CA 82:141853k) discusses the recovery of cellulose esters used as film supports. In this patent, he took processed film that has had the image layers removed and then processed this material to recover the cellulose acetate (unspecified degree of substitution).
S. G. Tereshkova et al. disclose a method of restoring triacetate base of cine film (S. G. Tereshkova, E. A. Prodan, O. P. Ol'shevskaya, I. S. Panchev, SU 1,282,064 (1987): CA 107:31144g). This is a multistep process that used aqueous sulfuric acid, water (steam), and acetone to remove the image layers from photographic film. The final DS and form of the film is not mentioned.
The extrusion of "worn out" triacetate photo graphic films is disclosed by L. G. Tovkalo et al (L. G. Tovkalo, 0. A. Fridman, L. N. Malinin, Plast. Massy., (7) 54 (1982): CA 97:110935u). The films are plasticized and extruded at 230.degree. C. to produce reels or cassettes.
Fuji Photo Film Co., Ltd., of Japan disclosed the recycling of photographic films (JP 55118829 (1980): CA 94:93566t). In this patent, they discuss the embossing of scrap films prior to removing the emulsion layers in an "appropriate solution."
It is well known in the art that CDAs may be prepared by the hydrolysis or methanolysis of CTA; however, this type chemistry has not been applied to processed film base containing plasticizers, gelatin, dyes, and the like. The hydrolysis of cellulose triacetate has been carried out in acetic acid with no catalyst (L. A. Hiller, J. Polymer Science, 10, pp. 385-423 (1953)) with strong acid catalysts (H. Yabune, Y. Ikemoto, Y. Kato, M. Uchiada, U.S. Pat. No. 4,439,605 (1984) and K. C. Campbell, J. M. Davis, R. E. Woods, Jr., U.S. Pat. No. 3,767,642 (assigned to Celanese Corporation) (1973)), and where the strong acid catalyst was neutralized prior to hydrolysis (U.S. Pat. No. 4,269,972). None of these processes start with processed film.
Since the above processes for recycling processed film are multistep processes (removing emulsion followed by further treatment), there is a need for a one step, economical process to convert processed CTA film into a useful material such as CDA. This process must remove the gelatin, plasticizer, dyes, and other extraneous materials in the processed film. The process should be robust enough to handle materials from various sources without causing processing problems. The conditions of hydrolysis should not be severe enough to cause substantial molecular weight degradation of the polymer.